Fix Firefox's memory problems, says Mozilla director

Mozilla must address Firefox's memory problems if it's serious about entering the mobile browser market, a member of the company's board of directors said over the weekend.

The on-again, off-again debate over whether Firefox has a memory leak was dragged back into the limelight by Christopher Blizzard, a Red Hat developer and longtime contributor to Firefox who also sits on Mozilla's board. "As Mozilla starts down the path to running in the mobile space we are spending time looking at memory pressure issues more closely," Blizzard said in a posting to his personal blog on Saturday, referring to the leak that many users believe plagues Firefox.

The longer Firefox runs and more pages it opens, the theory goes, the larger its appetite for memory. At some point, the load is significant enough to hinder performance or in some cases, lock the browser. But closing tabs doesn't reclaim the memory; only shutting down the browser and restarting does.

Blizzard stopped short of calling the leak a feature, as other Firefox developers have in the past, but neither did he embrace the idea that one really exists. "It sounds like the early data suggests that Mozilla really doesn't leak that much memory at all," he said. "But it does thrash the [memory] allocator pretty hard and that's what causes the perception of memory leaks."

Even bringing up the idea of a memory leak was enough to bring out users who swore it was a reality, not just a perception. "I don't know if Mozilla actually leaks memory, but it's performance certainly degrades with use," said a user identified as sb in a comment to Blizzard's blog. "My browser is nice and snappy right at startup, taking [a] 600MB footprint. After 3 days of intensive use, it's up to a 1.1GB footprint, no big deal but it often locks up for multiple seconds."

According to tests run by another Firefox developer, Stuart Parmenter, the issue isn't so much an actual leak, but one of memory fragmentation, where large amounts of free memory are scattered between small blocks of used memory. "It makes it very difficult for us to get big chunks of contiguous memory to give back to the OS," said Parmenter. "This makes us look big!"

Whether the leak is real and measurable or as Parmenter speculated, more fragmentation than true leak, Blizzard tied work on the problem to Mozilla's move into the mobile market, which currently is dominated by Opera Software ASA's Opera Mini. Apple, which this summer introduced a mobile edition of its Safari browser in the iPhone -- and more recently, in the iPod touch -- would also be a mobile rival to Mozilla. "Over the next few months it will be very interesting to see what happens with both memory usage and perceived performance especially as we connect numbers to a successful mobile strategy," said Blizzard.

That in itself came in for criticism from at least a few Firefox users. "So basically what you're saying is that you didn't really care about the problem until you went into the mobile space, where the problem was going to lose you money," said Karl Shea in another comment appended to Blizzard's post. "Memory leaks, fragmentation, or whatever the real problem is has been a problem since 1.0. Well, I'm glad financial matters finally pushed the issue."

Blizzard rebutted Shea a few comments later. "Mobile is a factor, but it's certainly not the main driver. We know that [will] this have a positive impact in both desktop users and mobile so it's worth the investment."

Mozilla's embryonic mobile strategy hasn't been officially spelled out, but Jay Sullivan, a mobile software developer recently hired by the company, has posted several entries in the last two weeks, including one titled "Mobile and the Mozilla manifesto," where he argues for taking Firefox mobile.

"My read on the Mozilla manifesto tells me that there's not only an opportunity presented by mobile, but that we have a responsibility to help crack open the mobile environment," said Sullivan.

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